//
// SJA1000 CAN 控制器外设实现（简化版，支持接收队列，可配置长度）
// 仅支持 PeliCAN 模式的标准帧，不考虑 BasicCAN、扩展帧、错误处理、多帧、验收滤波和发送中断。
// 寄存器地址映射基于 PeliCAN 模式，包含 MOD, CMR, SR, IR, IER, BTR0, BTR1, OCR, RXERR, TXERR,
// 发送缓冲区（地址 16-26）、RBSA 和 CDR。命令寄存器位2=RRB，位3=CDO。
// 所有寄存器可随时读写，无复位模式限制。
//
// 接收队列长度可通过修改静态字段 MaxRxQueueSize 调整。
// 接收队列满时，外部注入的新帧被丢弃。
//
// 发送采用立即发送模式（无波特率延迟），每帧发送完成后触发 FrameTransmitted 事件并转发到 TCP 客户端。
// TCP Server 为静态共享实例，监听端口 10000，将发送的帧数据转发给所有连接的客户端。
// 日志开关：EnableVerboseLog = false 可关闭所有日志输出。
// 实现了 IDisposable 接口，TCP 服务器由所有实例共享，仅当最后一个实例销毁时停止服务器。
//

using System;
using System.Text;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
using Antmicro.Renode.Core;
using Antmicro.Renode.Logging;
using Antmicro.Renode.Peripherals.Bus;
using Antmicro.Renode.Utilities;
using Antmicro.Renode.Time;

namespace Antmicro.Renode.Peripherals.CustomPeripherals
{
    /// <summary>
    /// 简化版 SJA1000 CAN 控制器（PeliCAN 模式，仅标准帧，立即发送，TCP 转发）
    /// </summary>
    public class SJA1000_CAN : IDoubleWordPeripheral, IBytePeripheral, IKnownSize, IDisposable
    {
        // 日志开关（设置为 false 可屏蔽所有日志）
        public static bool EnableVerboseLog = false;

        // 接收队列长度配置（可修改）
        public static int MaxRxQueueSize = 64;   // 接收队列最大帧数

        // 发送事件：当一帧数据被发送时触发
        public event Action<byte[]> FrameTransmitted;

        // ================ 静态 TCP Server 共享资源 ================
        private static TcpListener sharedTcpListener;
        private static readonly List<NetworkStream> sharedTcpClients = new List<NetworkStream>();
        private static readonly object sharedTcpLock = new object();
        private static CancellationTokenSource sharedTcpCts;
        private static Task sharedTcpServerTask;
        private static int sharedTcpRefCount = 0;   // 引用计数
        private bool disposed = false;
  
        public SJA1000_CAN(IMachine machine)
        {
            this.machine = machine;
            IRQ = new GPIO();

            txBuffer = new byte[11];
            rxBuffer = new byte[11];
            rxFrameQueue = new Queue<byte[]>();

            // 启动共享 TCP Server（增加引用计数）
            StartSharedTcpServer();

            Reset();
        }

        public void Reset()
        {
            mod = 0;
            ier = 0;
            btr0 = 0;
            btr1 = 0;
            ocr = 0;
            rxerr = 0;
            txerr = 0;
            rbsa = 0;
            cdr = 0;

            sr_tbs = 1;      // 发送缓冲区始终空闲（立即发送模式）
            sr_rbs = 0;      // 接收缓冲区初始为空
            ir = 0;

            Array.Clear(txBuffer, 0, txBuffer.Length);
            Array.Clear(rxBuffer, 0, rxBuffer.Length);
            rxFrameQueue.Clear();

            lastInterruptState = false;
            UpdateInterrupts();

            if (EnableVerboseLog)
                this.Log(LogLevel.Info, $"SJA1000 CAN controller reset (rxQueueMax={MaxRxQueueSize})");
        }

        // ================ 共享 TCP Server 管理 ================
        private void StartSharedTcpServer()
        {
            lock (sharedTcpLock)
            {
                sharedTcpRefCount++;
                if (sharedTcpRefCount > 1)
                {
                    if (EnableVerboseLog)
                        Console.WriteLine("TCP Server already running, using existing instance.");
                    return;
                }
                // 确保之前的已停止（安全）
                StopSharedTcpServerInternal();
                sharedTcpCts = new CancellationTokenSource();
                sharedTcpServerTask = Task.Run(() => TcpServerLoop(sharedTcpCts.Token), sharedTcpCts.Token);
                if (EnableVerboseLog)
                    Console.WriteLine("TCP Server started on port 10000 (shared)");
            }
        }

        private void StopSharedTcpServer()
        {
            lock (sharedTcpLock)
            {
                if (sharedTcpRefCount > 0)
                    sharedTcpRefCount--;
                if (sharedTcpRefCount > 0)
                {
                    if (EnableVerboseLog)
                        Console.WriteLine("TCP Server still in use, not stopping.");
                    return;
                }
                StopSharedTcpServerInternal();
            }
        }

        private static void StopSharedTcpServerInternal()
        {
            if (sharedTcpCts != null)
            {
                sharedTcpCts.Cancel();
                try { sharedTcpServerTask?.Wait(1000); } catch { }
                sharedTcpCts.Dispose();
                sharedTcpCts = null;
                sharedTcpServerTask = null;
            }
            if (sharedTcpListener != null)
            {
                try { sharedTcpListener.Stop(); } catch { }
                sharedTcpListener = null;
            }
            lock (sharedTcpLock)
            {
                foreach (var s in sharedTcpClients)
                    s?.Close();
                sharedTcpClients.Clear();
            }
            if (EnableVerboseLog)
                Console.WriteLine("TCP Server stopped.");
        }

        private static void TcpServerLoop(CancellationToken token)
        {
            try
            {
                sharedTcpListener = new TcpListener(IPAddress.Any, 10000);
                sharedTcpListener.Server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
                sharedTcpListener.Start();
                while (!token.IsCancellationRequested)
                {
                    var clientTask = sharedTcpListener.AcceptTcpClientAsync();
                    clientTask.Wait(token);
                    if (clientTask.IsCompleted && !token.IsCancellationRequested)
                    {
                        var client = clientTask.Result;
                        var stream = client.GetStream();
                        lock (sharedTcpLock)
                        {
                            sharedTcpClients.Add(stream);
                        }
                        if (EnableVerboseLog)
                            Console.WriteLine($"TCP client connected from {client.Client.RemoteEndPoint}");
                    }
                }
            }
            catch (OperationCanceledException) { }
            catch (Exception ex)
            {
                if (EnableVerboseLog)
                    Console.WriteLine($"TCP Server error: {ex.Message}");
            }
            finally
            {
                sharedTcpListener?.Stop();
                lock (sharedTcpLock)
                {
                    foreach (var s in sharedTcpClients)
                        s?.Close();
                    sharedTcpClients.Clear();
                }
            }
        }

        private void BroadcastFrame(byte[] frame)
        {
            if (frame == null || frame.Length != 11) return;
            lock (sharedTcpLock)
            {
                var clients = sharedTcpClients.ToArray();
                foreach (var stream in clients)
                {
                    try
                    {
                        stream.Write(frame, 0, frame.Length);
                        stream.Flush();
                    }
                    catch (Exception ex)
                    {
                        if (EnableVerboseLog)
                            Console.WriteLine($"Failed to send frame to client: {ex.Message}");
                        sharedTcpClients.Remove(stream);
                        stream.Close();
                    }
                }
            }
        }

        // ================ IBusPeripheral 接口实现（完全不变） ================

        public uint ReadDoubleWord(long offset) => ReadByte(offset);
        public void WriteDoubleWord(long offset, uint value) => WriteByte(offset, (byte)value);

        public byte ReadByte(long offset)
        {
            byte value = 0;
            lock (lockObject)
            {
                switch ((Registers)offset)
                {
                    case Registers.MOD:
                        value = mod;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read MOD: 0x{0:X2}", value);
                        break;

                    case Registers.CMR:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read CMR (always 0)");
                        value = 0;
                        break;

                    case Registers.SR:
                        value = (byte)((sr_tbs << 2) | sr_rbs);
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read SR: TBS={0}, RBS={1} -> 0x{2:X2}", sr_tbs, sr_rbs, value);
                        break;

                    case Registers.IR:
                        value = ir;
                        ir = 0;
                        UpdateIrFromRbs();
                        lastInterruptState = false;
                        UpdateInterrupts();
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read IR: 0x{0:X2}, cleared", value);
                        break;

                    case Registers.IER:
                        value = ier;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read IER: 0x{0:X2}", value);
                        break;

                    case Registers.BTR0:
                        value = btr0;
                        break;
                    case Registers.BTR1:
                        value = btr1;
                        break;
                    case Registers.OCR:
                        value = ocr;
                        break;
                    case Registers.RXERR:
                        value = rxerr;
                        break;
                    case Registers.TXERR:
                        value = txerr;
                        break;
                    case Registers.RBSA:
                        value = rbsa;
                        break;
                    case Registers.CDR:
                        value = cdr;
                        break;

                    case Registers.TX_FRAME_INFO:
                    case Registers.TX_ID1:
                    case Registers.TX_ID2:
                    case Registers.TX_DATA1:
                    case Registers.TX_DATA2:
                    case Registers.TX_DATA3:
                    case Registers.TX_DATA4:
                    case Registers.TX_DATA5:
                    case Registers.TX_DATA6:
                    case Registers.TX_DATA7:
                    case Registers.TX_DATA8:
                        int bufIndex = (int)(offset - (long)Registers.TX_FRAME_INFO) / 4;
                        if (sr_rbs == 1)
                        {
                            value = rxBuffer[bufIndex];
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Read RX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        else
                        {
                            value = txBuffer[bufIndex];
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Read TX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        break;

                    default:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Read from unimplemented offset 0x{0:X}", offset);
                        value = 0;
                        break;
                }
            }
            return value;
        }

        public void WriteByte(long offset, byte value)
        {
            lock (lockObject)
            {
                switch ((Registers)offset)
                {
                    case Registers.MOD:
                        mod = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write MOD: 0x{0:X2}", value);
                        break;

                    case Registers.CMR:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write CMR: 0x{0:X2}", value);
                        if ((value & CMR_TR) != 0)
                        {
                            // 发送请求（立即发送模式）
                            if (sr_tbs == 1)
                            {
                                // 复制当前帧
                                byte[] frame = new byte[11];
                                Array.Copy(txBuffer, frame, 11);
                                // 清空发送缓冲区（准备下一帧）
                                Array.Clear(txBuffer, 0, txBuffer.Length);

                                // 立即发送帧数据
                                FrameTransmitted?.Invoke(frame);
                                BroadcastFrame(frame);

                                // 保持发送缓冲区空闲（始终允许写入）
                                sr_tbs = 1;

                                if (EnableVerboseLog) this.Log(LogLevel.Info, "Frame transmitted immediately");
                            }
                            else
                            {
                                if (EnableVerboseLog) this.Log(LogLevel.Warning, "Send request while TBS=0 ignored");
                            }
                        }
                        if ((value & CMR_RRB) != 0)
                        {
                            // 释放接收缓冲器
                            sr_rbs = 0;
                            UpdateIrFromRbs();
                            UpdateInterrupts();
                            LoadNextRxFrame();
                            UpdateInterrupts();
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Receive buffer released");
                        }
                        if ((value & CMR_CDO) != 0)
                        {
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Clear data overflow (no effect)");
                        }
                        break;

                    case Registers.SR:
                        if (EnableVerboseLog) this.Log(LogLevel.Warning, "Attempted write to read-only SR");
                        break;

                    case Registers.IR:
                        if (EnableVerboseLog) this.Log(LogLevel.Warning, "Attempted write to read-only IR");
                        break;

                    case Registers.IER:
                        ier = (byte)(value & 0x01);
                        UpdateIrFromRbs();
                        UpdateInterrupts();
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write IER: 0x{0:X2}", ier);
                        break;

                    case Registers.BTR0:
                        btr0 = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write BTR0: 0x{0:X2}", value);
                        break;
                    case Registers.BTR1:
                        btr1 = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write BTR1: 0x{0:X2}", value);
                        break;
                    case Registers.OCR:
                        ocr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write OCR: 0x{0:X2}", value);
                        break;
                    case Registers.RXERR:
                        rxerr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write RXERR: 0x{0:X2}", value);
                        break;
                    case Registers.TXERR:
                        txerr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write TXERR: 0x{0:X2}", value);
                        break;
                    case Registers.RBSA:
                        rbsa = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write RBSA: 0x{0:X2}", value);
                        break;
                    case Registers.CDR:
                        cdr = value;
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write CDR: 0x{0:X2}", value);
                        break;

                    case Registers.TX_FRAME_INFO:
                    case Registers.TX_ID1:
                    case Registers.TX_ID2:
                    case Registers.TX_DATA1:
                    case Registers.TX_DATA2:
                    case Registers.TX_DATA3:
                    case Registers.TX_DATA4:
                    case Registers.TX_DATA5:
                    case Registers.TX_DATA6:
                    case Registers.TX_DATA7:
                    case Registers.TX_DATA8:
                        int bufIndex = (int)(offset - (long)Registers.TX_FRAME_INFO) / 4;
                        if (sr_tbs == 1)
                        {
                            txBuffer[bufIndex] = value;
                            if (EnableVerboseLog) this.Log(LogLevel.Info, "Write TX buffer[{0}]: 0x{1:X2}", bufIndex, value);
                        }
                        else
                        {
                            if (EnableVerboseLog) this.Log(LogLevel.Warning, "Write to TX buffer while TBS=0 ignored");
                        }
                        break;

                    default:
                        if (EnableVerboseLog) this.Log(LogLevel.Info, "Write to unimplemented offset 0x{0:X} = 0x{1:X2}", offset, value);
                        break;
                }
            }
        }

        // ================ 接收与中断管理 ================
        private void UpdateIrFromRbs()
        {
            if (sr_rbs == 1)
                ir |= IR_RI;
            else
                ir = (byte)(ir & ~IR_RI);
        }

        private void UpdateInterrupts()
        {
            bool currentInterrupt = ((ir & IR_RI) != 0) && ((ier & IER_RIE) != 0);
            if (currentInterrupt && !lastInterruptState)
            {
                IRQ.Set(true);
                machine.ScheduleAction(TimeInterval.FromMicroseconds(1), _ => IRQ.Set(false));
                if (EnableVerboseLog) this.Log(LogLevel.Info, "Interrupt pulse generated (RI)");
            }
            lastInterruptState = currentInterrupt;
        }

        private readonly object lockObject = new object();
        private bool lastInterruptState;

        /// <summary>
        /// 获取接收队列中所有帧的字符串表示（每帧以空格分隔的十六进制字节，帧间用换行分隔）
        /// 注意：此方法仅用于调试，会影响接收队列。
        /// </summary>
        public string GetRxBufferDataString()
        {
            lock (lockObject)
            {
                if (rxFrameQueue.Count == 0)
                {
                    if (EnableVerboseLog) Console.WriteLine("GetRxBufferDataString: no frames in RX queue");
                    return null;
                }
                var sb = new StringBuilder();
                while (rxFrameQueue.Count > 0)
                {
                    var frame = rxFrameQueue.Dequeue();
                    for (int i = 0; i < frame.Length; i++)
                    {
                        if (i > 0) sb.Append(" ");
                        sb.Append(frame[i].ToString("X2"));
                    }
                    sb.AppendLine();
                }
                string result = sb.ToString().TrimEnd();
                if (EnableVerboseLog) Console.WriteLine("GetRxBufferDataString returning: " + result);
                return result;
            }
        }

        /// <summary>
        /// 外部接口注入一帧接收数据（可变长度的十六进制字符串，空格分隔）
        /// 可多次调用以注入多帧，帧将存入接收队列。
        /// 若接收队列已满，则新帧被丢弃。
        /// 输入字符串长度可变（0~11 字节），不足 11 字节时自动补零，超出 11 字节时截断并警告。
        /// </summary>
        public void SendRxBufferDataString(string frameString)
        {
            lock (lockObject)
            {
                if (string.IsNullOrWhiteSpace(frameString))
                {
                    if (EnableVerboseLog) Console.WriteLine("SendRxBufferDataString: empty string, ignored");
                    return;
                }
                string[] parts = frameString.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                int length = parts.Length;
                if (length > 11)
                {
                    if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: input has {length} bytes, truncating to 11");
                    length = 11;
                }

                byte[] frame = new byte[11];
                for (int i = 0; i < length; i++)
                {
                    string part = parts[i].Trim();
                    if (!byte.TryParse(part, System.Globalization.NumberStyles.HexNumber,
                        System.Globalization.CultureInfo.InvariantCulture, out byte b))
                    {
                        if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: invalid hex byte '{part}' at index {i}, set to 0");
                        b = 0;
                    }
                    frame[i] = b;
                }

                if (rxFrameQueue.Count >= MaxRxQueueSize)
                {
                    if (EnableVerboseLog) Console.WriteLine($"SendRxBufferDataString: RX queue full, frame dropped");
                    return;
                }

                rxFrameQueue.Enqueue(frame);
                if (EnableVerboseLog) Console.WriteLine($"Frame enqueued to RX queue, size: {rxFrameQueue.Count}");

                if (sr_rbs == 0)
                {
                    LoadNextRxFrame();
                    UpdateInterrupts();
                }
            }
        }

        private void LoadNextRxFrame()
        {
            if (rxFrameQueue.Count > 0)
            {
                var frame = rxFrameQueue.Dequeue();
                Array.Copy(frame, rxBuffer, 11);
                sr_rbs = 1;
                UpdateIrFromRbs();
                if (EnableVerboseLog) Console.WriteLine("Loaded next RX frame, remaining: {0}", rxFrameQueue.Count);
            }
            else
            {
                sr_rbs = 0;
                UpdateIrFromRbs();
                if (EnableVerboseLog) Console.WriteLine("RX queue empty, buffer cleared");
            }
        }

        // ================ IDisposable 实现 ================
        public void Dispose()
        {
            if (!disposed)
            {
                StopSharedTcpServer();   // 减少引用计数，可能停止服务器
                disposed = true;
            }
            GC.SuppressFinalize(this);
        }

        ~SJA1000_CAN()
        {
            Dispose();
        }

        // ================ 属性 ================

        public long Size => 0x80;
        public GPIO IRQ { get; }

        // ================ 寄存器枚举 ================
        private enum Registers : long
        {
            MOD = 0x00,
            CMR = 0x04,
            SR = 0x08,
            IR = 0x0C,
            IER = 0x10,
            BTR0 = 0x18,
            BTR1 = 0x1C,
            OCR = 0x20,
            RXERR = 0x38,
            TXERR = 0x3C,
            TX_FRAME_INFO = 0x40,
            TX_ID1 = 0x44,
            TX_ID2 = 0x48,
            TX_DATA1 = 0x4C,
            TX_DATA2 = 0x50,
            TX_DATA3 = 0x54,
            TX_DATA4 = 0x58,
            TX_DATA5 = 0x5C,
            TX_DATA6 = 0x60,
            TX_DATA7 = 0x64,
            TX_DATA8 = 0x68,
            RBSA = 0x78,
            CDR = 0x7C,
        }

        // ================ 常量位定义 ================
        private const byte CMR_TR = 0x01;
        private const byte CMR_RRB = 0x04;
        private const byte CMR_CDO = 0x08;

        private const byte SR_TBS = 0x04;
        private const byte SR_RBS = 0x01;

        private const byte IR_RI = 0x01;
        private const byte IER_RIE = 0x01;

        // ================ 私有字段 ================
        private readonly IMachine machine;

        private byte mod;
        private byte ier;
        private byte btr0, btr1;
        private byte ocr;
        private byte rxerr, txerr;
        private byte rbsa;
        private byte cdr;

        private byte sr_tbs;
        private byte sr_rbs;
        private byte ir;

        private readonly byte[] txBuffer;
        private readonly byte[] rxBuffer;

        private readonly Queue<byte[]> rxFrameQueue;   // 仅接收队列
    }
}